#include <stdio.h>
#include <unistd.h>

int g_val = 100;

int main()
{

    pid_t id = fork();
    if (id == 0)
    {   
        int cnt = 0;
        //child
        while (1)
        {
            printf("I am child,pid: %d, ppid:%d, g_val：%d, &g_val: %p\n", getpid(), getppid(), g_val, &g_val);
            sleep(1);
            cnt++;
            if (cnt == 5)
            {
                g_val = 200;
                printf("child change g_val 100 -> 200 success\n");
            }
        }
    }
    else 
    {    
        //father
        while(1)
        {
            printf("I am father,pid: %d, ppid:%d, g_val：%d, &g_val: %p\n", getpid(), getppid(), g_val, &g_val);
            sleep(1);

        }
    }

    return 0;
}
